In the field of fluid hydraulics, the need for pressure intensifiers and reducers is well known. One type of pressure intensifier utilizes external mechanical elements which act on the hydraulic fluid to increase its energy content and pressure. One type of pressure reducer is a pressure regulator which utilizes external mechanical control elements to absorb or control the flow rate of the hydraulic fluid in order to reduce its energy content and pressure.
Another well known type of pressure intensifier or reducer involves an assembly of pistons in hich each piston includes at least two opposing surfaces of different surface areas. By applying pressure to the smaller surface, the resulting force on the piston creates a reduced pressure at the larger surface. By applying pressure to the larger surface, an increased pressure results at the smaller surface. Piston-type intensifiers and reducers have the advantage of preserving the energy content of the fluid while inherently performing pressure amplification or reduction. Piston-type intensifiers and reducers are preferred over the other types of devices involving external control elements because of the reliability and predictability associated with inherent operation.
To obtain multiple increments of pressure reduction or intensification requires the use of multiple separate pistons serially connected together. Each piston in the series operates independently of the others, and each receives its input pressure from the preceding piston and supplies its output pressure to the following piston. Each piston in the series therefore creates its own independent influences on the overall performance of the system. Because of the serial connection and the independent influences of each, some difficulty exists in obtaining certain desired and controllable effects such as predetermined pressure increments across the seal elements used in the series.
In the field of fluid seal assemblies, which are used for sealing static or dynamically moving parts against the application of pressure differentials, there are no known reliable and economic seal elements which remain effective against the application of extremely high pressure differentials. Seal failure is directly related to the magnitude of the pressure differential which the seal must withstand. High pressure seals typically fail after a relatively short period of use because they are characteristically unable to withstand extremely high pressure differentials, particularly when relative movement between the seal element and one of the parts to be sealed is involved. Even when a plurality of seals are ganged or connected together, the majority of the pressure differential is typically withstood by only one seal of the group. No effective means is known to exist for deriving and maintaining equal or predetermined pressure intervals or divisions between each of the seals in the group whereby each seal is required to maintain only a predetermined fraction of the pressure differential to allow the whole group of seals to remain effective against extremely high pressures for a considerable period of use.
In the field of linear actuators, pumps and other types of fluid hydraulic movement devices, mechanical movement is derived or controlled from pressure application to pistons. The pistons may be of the pressure intensifier or reducer type, and a number of pistons may be connected in series to obtain multiplied or reduced amounts of mechanical movement from the last or output piston as compared to the amount of movement of the input or first piston obtained from pressure alplication. The amount of output piston movement varies in accordance with an exponential multiplier depending on the number of series connected pistons. Relatively large piston movements are obtained from relatively small input pressure changes in devices obtaining increased output piston movement as compared to input piston movements. Relatively small Piston movements are obtained from relatively large input pressure changes in devices obtaining reduced output piston movement as compared to input piston movement. While such radical variations in output movement and pressure compared to input pressure or movement may be desired in some situations, more uniform and smoother transitions between input pressure and output movement, or vice versa, are desired but have been previously unavailable in prior art series connected piston assemblies.